With sedation and sleeping pills increasingly common staples of the American medicine cabinet, are we legally accountable for crimes committed during sleepy hazes? Should we be held accountable? Theresa Fisher asks the legal and psychological experts who are wrestling with these issues every day.

In 2008, Vernon Silich, then a 42-year-old taxi driver in a suburb of Perth, Australia, entered his parents’ bedroom in the middle of the night and kicked them both to death. Silich and his father had spent the night drinking heavily following the funeral of Silich’s brother, who’d died of a drug overdose. Early the next morning, Silich came upon his parents’ bodies — which he’d rearranged so they lay hand-in-hand — without any recollection of what he’d done.

Two years later, Silich pled “not guilty” to willful murder before a 10-person jury. He may have killed his parents, the defense maintained, but he wasn’t culpable because he wasn’t in a legally conscious state — he’d been sleepwalking, a recurring habit since childhood.

Two sleep experts testified on Silich’s behalf. But the jury still returned a guilty verdict that resulted in a life sentence.

“The whole doggone thing made my blood boil,” says Rosalind Cartwright, a Chicago-based sleep scientist in her 90s and proponent of sleepwalking as a viable criminal defense. Silich, she believes, should not be held criminally accountable for his actions.

Unfortunately for Silich, his team failed to make the case. “They had two sleep experts,” Cartwright says, “and neither of them was up to speed.”

The problem is, in the field of sleep forensics, the meaning of being “up to speed” still isn’t clear.

Sleepwalking Through History

Nineteenth-century psychiatrist Benjamin Rush thought of sleepwalking as a type of delirium caused by “morbid or irregular action in the blood-vessels of the brain.” Today, we know that the sleepwalking brain is basically stuck in a confused hybrid of wakefulness and deep sleep (or Slow Wave Sleep).

Since 1987, the Diagnostic and Statistical Manual of Mental Disorders has listed sleepwalking disorder as a parasomnia, a class of arousal sleep disorders that includes sleep-eating, sleep-sex, sleep-driving and nocturnal wandering. It typically occurs early in the night. Whereas normal sleepers pass out hard during deep sleep, true sleepwalkers are easily aroused by minor disruptions.

For reasons still being explored, some people are predisposed to sleepwalking, and may wrestle with it their entire lives. Other parasomnic states — from harmless, odd behavior to more drastic, potentially dangerous behaviors — may be triggered by stress, environmental disturbances and drugs — both legal and illicit.

The sleepwalking defense formally entered American jurisprudence in the 19th century. At the time, doctors and legal experts recognized sleepwalking as a qualitatively different state of consciousness, such that people in the throes of a parasomnia episode lacked the free will necessary for culpability. But courtroom efforts to distinguish true sleepwalkers from malingering criminals faltered between common sense analyses, character assessments and total crapshoots.

“You don’t know what the heck you’re doing, but you can get into lots, and lots, of trouble.”

The country’s first successful sleepwalking defense was fielded by the defense team of Albert Tirrell, a Massachusetts family man accused of murdering Maria Bickford, the raven-haired prostitute of his dreams, in 1846. Tirrell’s attorney argued that, if Tirrell had indeed killed Bickford, he’d done so during a nightmare.

A psychiatrist testified that Tirrell deserved an acquittal because he wasn’t consciously aware of what he was doing. The jury was urged to consider somnambulism as equivalent to insanity, and thus grounds for acquittal. The gambit worked: Tirrell was not held accountable for decapitating Bickford, nor for burning down her brothel. He was found guilty of adultery.

If the Tirrell case helped bring sleep crimes into the common law, it also highlighted the fundamental problem: It’s impossible to know, with complete certainty, whether or not a defendant was actually sleepwalking at the time of their alleged offense. Within a decade of Tirrell’s overall adultery conviction, experts — including the father of forensic psychiatry, Isaac Ray — began developing guidelines for identifying sleepwalkers. In 1853, Ray wrote:

“As a somnambulist does not enjoy the free and rational exercise of his understanding, and is more or less unconscious of his outward relations, none of his acts during the paroxysms, can rightfully be imputed to him as crimes.”

Ray was also fully aware of the implications of a successful sleepwalking defense. He cautioned:

“Once acquit a criminal on the score of somnambulism which is imperfectly or at best but plausibly proved, and it will soon become a favorite excuse for crime, whenever the offender possesses the requisite address for maintaining the deception”

To help codify the condition, Ray drew up a portrait of the “authentic” parasomniac who wakes up astonished, concerned and remorseful. In 1974, the Canadian researcher Alexander Bonkalo published a more thorough set of criteria to confirm somnambulism. They include:

The person attacked was well-loved by the attacker.There was profound amnesia for the event.There was no apparent motivation for the attack.There was no attempt to cover up the crime.The accused had a history of childhood parasomnias substantiated by friends and relatives.There was no previous history of violence.

More than 40 years later, Bonkalo’s guidelines are still in use. Why is it so hard to diagnose sleepwalking and other parasomnias in a scientific fashion?

Problems with Profiling

“Let’s say, for argument’s sake, someone has a hundred episodes a day of narcolepsy, fell asleep at the wheel and killed somebody,” says Dr. Kenneth Weiss, a clinical professor of forensic psychiatry at the University of Pennsylvania. “Well, that’s about as good as you’re going to get. But some singular episode? You’re never going to catch it.”

It’s up to parasomnia experts like Dr. Cartwright to analyze criminal cases in which defendants invoke some version of the sleepwalking defense.

Dr. Cartwright and her peers face three fundamental challenges. First, despite scientific advancements, we still can’t be certain, in retrospect, whether someone was actually sleepwalking when they committed a crime. Second, we agree that people who are asleep lack moral agency, but we’re not exactly sure why. And, finally, we have trouble determining when parasomniacs deserve blame for behavior that induces their sleepwalking states. This last issue, in particular, has captured the public’s imagination as more Ambien-related crimes have reached American courtrooms.

If sleep crimes have a signature intoxicant, it’s Ambien.

According to Cartwright, Silich’s case is a textbook example of sleepwalking violence. He had no criminal history, but did have a history of sleepwalking. There was trauma. There was alcohol. On the night he killed his parents, Silich stayed up late before falling into a shallow sleep, disrupted by noise. Not long after dozing off, Silich got up and attacked his mother and father, whom, as news outlets covering his trial reported, and as Cartwright reiterated, Silich loved and treated well.

He had no inkling of his rampage until he found the bodies the next morning.

“What sleep deprivation does to the sleepwalker is that you have more pressure to get delta sleep,” said Cartwright. “Your poor brain is trying to get you to have good sleep and your neurological pattern is not allowing that to happen.”

Especially for those prone to sleepwalking, stimuli at this time — a dog barking, music coming from the room next door — causes a sleep-state push-pull. “The brain is trying to make more delta, the outside environment is trying to make you wake up,” said Cartwright, “and the push-pull between those two is what causes a disturbed brain system.”

The parasomniac’s body and lower emotional component of the brain are active, Cartwright explained, but the decision-making thought processes are still asleep.

“You don’t know what the heck you’re doing or why,” said Cartwright, “but you can move around and get into lots, and lots, of trouble.”

Sleepwalking Resists Science

Diagnosing sleeping disorders, in a clinical context, includes a behavioral assessment and, usually, a sleep test called polysomnography, which records brain wave activity during three consecutive nights of sleep. A number of sleep experts, however, resist using sleep tests in forensic analyses to avoid any false implication of scientific certainty.

At this point, sleep experts cannot retroactively certify whether someone sleepwalked at a specific time in the past, even if that person is a documented sleepwalker. Sleepwalking is episodic — and criminal culpability hinges on whether someone sleepwalked during a discrete time period, not whether they can claim sleepwalker status.

To avoid asserting false certainty, some sleep scientists prefer to make only modest claims during testimonies or avoid testifying entirely. Others resist incorporating sleep tests into their analysis, and instead rely purely on behavioral assessments, which fact-finders are less likely to misinterpret as objective proof of a past sleepwalking episode.

In her 90s, Cartwright is more pro-technology than the average sleep scientist. She actively promotes using spectral analysis, a highly detailed method for measuring deep sleep waves. In her view, competent expert testimony requires this sleep test when defendants play the sleep card.

But not all experts are in Cartwright’s camp, and plenty of others are a few decades shy of even taking a position. It’s not just technological distrust that hampers sleep forensics — it’s everything about the clunky fusion of sleep science and criminal law (and the morally squishy decisions that accompany it).

After taking on Silich’s case, Cartwright used spectral analysis to confirm her hunch: His delta waves were just as shallow and disrupted as a chronic sleepwalker’s should be. Cartwright, who’s writing up Silich’s case study now, said she hopes to get him clemency.

But Cartwright’s use of spectral analysis has ruffled some feathers. The problem, according to one group of researchers, is her overstating the forensic value of spectral analysis. They also maintained that Silich’s time in prison influenced the results. In their critique, they wrote, “Sleep in prison often results in significantly different sleep/wake schedules and patterns, sleep durations, absence of drug and alcohol effects, and weight loss.”

In Cartwright’s view, the time lapse and environmental change were irrelevant; she wasn’t looking to catch Silich in an episode. (Only one sleep study, from 2000, has successfully caught a subject mid-episode.) She did use sleep deprivation, but only because she’s looking for sleep wave patterns distinct to those predisposed to sleepwalking.

At least they’re having the debate. While the illusion of airtight proof burdens forensic science across the board, experts in the field don’t have the best track record in acknowledging their susceptibility to making mistakes. Studies have shown how easily experts can misinterpret fingerprints and other types of seemingly hard evidence. The FBI and Justice Department, as the Washington Post reported in April, finally owned up to using flawed forensic testimony in more than 250 convictions (including 32 capital death sentences) before the year 2000.

The Age of Ambien

Legal experts differ about why sleepwalking is an absolute defense to legal responsibility. The bones of criminal law provide a framework for analyzing guilt, but sleepwalking is a square peg.

Every crime has two elements: the actus reus, the physical act itself, and mens rea, the guilty mind behind the act. To be culpable, one must both intend to commit a crime and then voluntarily commit it. Is a sleeping person immune from guilt because they lack the state of mind necessary to form intent (mens rea)? Are they not accountable because, without consciousness, they can’t perform voluntary actions (actus reus)? Whether sleepwalking speaks to the mens rea or actus reus seems not to matter all that much in court.

Adjust your dose, or face blame for erratic sleep behavior.

Even within the U.S., statutory and case law offer a few different ways to understand sleep crimes. Sleepwalkers have plead not guilty on account of unconsciousness, automatism (involuntary actions) and insanity, the latter having fallen out of fashion. The conceptual differences between defenses may not be that relevant in practice. If defendants can convince a jury (or judge) that they most likely sleepwalked, Weiss said, it may not matter which legal defense they use to avoid responsibility. But, it often does matter what triggered their sleepwalking in the first place, especially if they happened to take sleeping medication.

If sleep crimes have a signature intoxicant, it’s Ambien, America’s favorite hypnotic sleeping pill. Ambien (and the generic version Zolpidem) is the most popular in its class of non-benzodiazepine sedatives, sometimes called “Z-Drugs.”

Ambien’s chemical structure makes it particularly well-suited for sleep. Like Xanax, Valium and other benzos, Ambien binds to the GABA receptors. But, unlike benzos, Ambien binds almost entirely with a single alpha-one receptor. As a result, Ambien causes amnesia and sedation without next-day drowsiness. Ambien can also cause a hypnotic, zombie-like state, similar to a non-drug-induced parasomnia episode.

Ambien was first approved by the FDA in 1992, but usage started to balloon in the mid-2000s, when the cheap generic version hit the market. Suddenly, Ambien was everywhere.

Then, the stories started rolling in. There was the Australian woman who habitually left her house during the night to have sex with strangers. And the 46-year-old woman who gained 50 pounds in a year from Ambien-fueled bingeing. Ambien DUI became one of the most common complaints, says Allen Trapp, a Georgia defense attorney who’s worked on hundreds of these cases. Trapp argued his first Ambien DUI case in 2006. Since then, prescription drug DUI arrests — featuring more than just Ambien — have shot up.

Trapp deals with two basic scenarios. The first concerns people who take their meds before bed, as they’re supposed to, but unknowingly rise in the middle of the night. They wake up in jell cells with no recollection of their mid-slumber antics. In the second case, people take their Ambien before running an errand, incorrectly assuming they’ll get home before the drug takes effect.

The problems became so widespread that, in 2007, the FDA required Z-Drug manufacturers to slap a warning on prescription bottles, specifying potential problems such as memory loss, having sex and eating unsavory combinations of food and non-food alike.

Clearly not enough people heed the FDA’s warning. Just ask Conrad Hilton III, hotel heir and little brother to Paris and Nicky, who freaked out on a transatlantic flight in July 2014. During his mile-high tirade, the 20-year-old threatened the pilot and crew, insulted fellow passengers and smoked pot in the bathroom. It took five flight attendants to restrain him. In a press statement, Hilton’s attorney, Robert Shapiro (of O.J. Simpson fame), attributed Hilton’s on-flight behavior to Ambien.

A Question of Culpability

One might assume that, once Ambien’s weird potential behaviors were codified by the FDA, the “Ambien Defense” would be an instant grand-slam. Not so.

Before the warning, people arrested for Ambien DUIs, for example, could argue that they had no way to foresee their strange behavior. After the warning came out, courts were less forgiving. After all, they’d been warned right there on the label. According to University of Vermont psychiatrist Christopher Daley, and the author of “I Did What?” Zolpidem and the Courts, as Ambien’s effects become more well-known, defendants will be expected to know what they can and can’t do after they pop an Ambi.

Then, last year, the FDA cut the recommended Ambien dosage from 10mgs to 5mgs due to concerns over the drug remaining in the blood long after ingestion. As a result, people who don’t adjust their doses accordingly will have a harder time in the courtroom sidestepping blame for erratic sleep behavior.

For those cases in which defendants claim their parasomnia was brought on by Ambien, they need to show that they took their medication responsibly. Taking Ambien to stay up and play video games, like one police officer did, registered somewhere below responsible. (It also didn’t do her any favors that, after she’d been fired, she repeatedly prank-called the police station while tripping on Ambien.) It’s not just degenerates who invite the jury’s wrath. In Texas in 2011, the court was unkind to an otherwise responsible middle-aged man whose wife accidentally included an Ambien in his morning pills. The court decided he’d taken his medication voluntarily and convicted him of driving while intoxicated.

And yet, on the other hand, there’s the 56-year-old Florida judge with no prior offenses who woke up slumped over her steering wheel outside the courthouse last year after reportedly taking Ambien for the first time. She got off easy.

It’s all very hard to predict, because we haven’t yet figured out how to handle repercussions from taking a prescription drug that causes adverse reactions but can also make anyone hallucinate under the right circumstances. Ambien, as of now, falls in a weird legal area, with one foot in intoxication and the other in parasomnia.

We might figure it out, but Daley suggested legal clarity may only come when the next generation of sleeping drugs inevitably ousts Z-Drugs from their throne. The newest prescription sleeping drug, called Belsomra, arrived on the market in February. Belsomra, manufactured by Merck, induces drowsiness through an entirely different neural pathway than its predecessors. It’s too early, however, to tell if Belsomra will become the next Ambien.

Despite 161 years of case law, the legal and moral implications of parasomniatic defenses are still very much up in the air. Even if Albert Tirrell were accused of killing Maria Bickford today, in a major American city, with all the benefits of modern forensics, his guilt would still hinge on one question: Do we believe him, or not?